Compositions and methods for transiently expressing proteins in a plant are provided. The compositions comprise plants, seeds, plant tissues, and plant parts expressing a protein, wherein the protein is expressed transiently and the transient expression of the protein can be used as a predictive model of how said protein will be expressed in stable transgenic plants in regards to qualitative and quantitative data. The predictive model may be used but is not limited to: promoter evaluation, evaluation of expression cassette construction for best performance (e.g. addition of enhancers or gene silencing suppressors), evaluation of best ways to express heterologous genes (e.g. point mutations, targeting), fast evaluation of endogenous gene knockout, evaluation of protein expression levels, cellular targeting, tissue targeting, transcriptional enhancers, translational enhancer protein toxicity and metabolic profiling. Further provided are methods of use.